Placental Transfer of Rh Antibody (Anti-D IgG) during Pregnancy

Abstract

Anti-D levels in blood taken immediately postpartum from Rh-negative women who have been given antenatal Rh immune globulin and the anti-D levels in the cord blood of their babies were measured semiquantitatively by a low ionic polybrene Auto Analyzer technique. When both mother and baby were Rh-negative a comparison of their anti-D levels was made against the interval between injection of the passive anti-D and delivery. Mothers’ levels decreased as the interval increased, the regression coefficient for 73 maternal sera was -0.74. The drop in levels of cord blood was much less than that of the mothers’ levels. The regression coefficient was -0.294 for 74 cord sera (one set of twins). The marked difference between cord blood and maternal blood levels of anti-D at delivery supports the hypothesis that the transfer of IgG across the placenta is predominantly from mother to fetus and not from fetus to mother.